{"id":3291,"date":"2021-08-27T18:09:27","date_gmt":"2021-08-27T06:09:27","guid":{"rendered":"http:\/\/blogs.lincoln.ac.nz\/gis\/?p=3291"},"modified":"2023-05-07T02:53:53","modified_gmt":"2023-05-07T02:53:53","slug":"level-4-exercise","status":"publish","type":"post","link":"https:\/\/blogs.lincoln.ac.nz\/gis\/level-4-exercise\/","title":{"rendered":"Level 4 Exercise"},"content":{"rendered":"

We use a bit of network analysis to set the extent of exercise during lockdown.<\/em><\/p>\n

So you now know that part of my coping strategy for lockdown is Stuff quizzes, but to be honest, the main strategy for me is exercise, and running in particular.\u00a0 I’d be lost without it, as those in my bubble well know.\u00a0 We are encouraged to get out and exercise so long as we keep it local, but what exactly does that mean?\u00a0 Is it my block?\u00a0 Is it my suburb?\u00a0 Is it my little South Island bach out in the middle of nowhere (which I of course went to before level 4, right?).\u00a0 It hasn’t been that explicit during this lockdown but in the previous one I do seem to recall a 5 kilometre distance being put on distances away from home that were acceptable.\u00a0 \u00a0You might not be too surprised that I was thinking about how I would use maps to help figure this out.\u00a0 So here goes!<\/p>\n

To demonstrate (and to protect my privacy…) I’ll created three points on a map to use for this – one in Beckenham, one in Governors Bay and one at the uni:<\/p>\n

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5 kilometres is a pretty distinct value to work with.\u00a0 If I know that I’m okay running within that distance from home, my first thought might be to just buffer around the point\u00a0is my start:<\/p>\n

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This gives me something to work with – sort of my running bubbles.\u00a0 To be fair, this is an as-the-kereru-flies distance, and, well, last time I tried to run through my neighbours back yard, he called the police.\u00a0 (I’m reminded\u00a0of John Cheever’s short story, The Swimmer<\/a>, where the protagonist decides to make his way home by swimming through all his neighbours’ pools to get there.)\u00a0 The reality is that we are constrained to use the road network for things like walking and running (and hopefully driving, too).\u00a0 So how do we take that into account?<\/p>\n

Here’s where Network Analysis<\/a> (NA) comes in to play.\u00a0 With the right input data, I can use NA to find the 5 k distances I can realistically travel along<\/em> the road network from a starting point.\u00a0 To get this to work in Pro we first need a dataset that’s been prepared for network analysis, meaning that, in the case of roads, each line segment has connectivity information\u00a0which ties it into the rest of the network, so that a pathway can be found from one point to another.\u00a0 There’s one in J:\\Data\\NetworkAnalysisData called RoadsNA_ND.\u00a0 Feel free to play along at home if you like.<\/p>\n

Next I created a new point feature class<\/a> for my starting points, added them to my map and created the three points you see above.\u00a0 What really matters in this layer is the geographic location so it really doesn’t need any attributes.<\/p>\n

Once I’ve got these layers added to my map, there’s now a Network Analysis<\/strong><\/span> button under the Analysis tab with a whole bunch of options beneath:<\/p>\n

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Routes is the same sort of thing you might do in Google Maps to get directions.\u00a0 I won’t go into the others this time, but for our purposes, what we’re after is Service Areas<\/a>.\u00a0 We’ve seen these before<\/a> here at GIS Central.\u00a0 Selecting that adds a new layer to my map:<\/p>\n

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In this new layer, Facilities are my starting points, the Polygon and Lines layers are my two potential output layers and the different barriers are ways of limiting connectivity – like road blocks.\u00a0 Next I need to set the layer that I’m using as my start points, here called (creatively) Facilities.\u00a0 The Import Facilities<\/span><\/strong> button allows me to set this to my Facilities layer:<\/p>\n

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A few of the other key settings:<\/p>\n